The present invention relates to a method and apparatus for removing form sand from a casting box and for comminuting any sand clods formed by the sand removed from the box.
The removal of form sand and the casting from a casting box has up to now been made in such a manner that the filled casting box has been placed with an open end onto a horizontally extending grate, which is vibrated in vertical direction, so that the form sand and the castings molded therein are separated from each other and from the casting box. Some of the sand particles removed from the box stick together, especially if a binder of plastic material is used for the sand particles, to form sand clods of various size. The smaller ones will fall through the grate and have to be subsequently comminuted in a special apparatus, but the larger ones accumulate on the upper grate surface and must be subsequently removed therefrom and be comminuted in corresponding comminuting apparatus.
While principally it is also possible to remove the form sand from a casting box also on a stationary grate, any sand clods which do not fall through the grate must be removed therefrom and subsequently be comminuted.
Even if vibrating grates are used, the large sand clods remaining thereon can be comminuted only with great difficulties, even though they vibrate with the grate, they will spread out on the horizontal upper surface of the grate and thus not rub against each other which would expedite the comminuting thereof. In addition, there is the danger that such sand clods will fall off laterally of the grate. On the other hand, the grates must have a horizontal plane upper surface so that the filled casting box may be properly received thereon.
Various devices are known in the art for comminuting sand clods removed from a casting box. Such devices are especially necessary if the form sand is intermixed with a binder of plastic material. As a rule such apparatus may comprise ball mills, hammer mills or integrators in which the clods are vibrated together with iron parts to comminute or disintegrate the clods. In using such known separate comminuting devices, the sand clods have to be removed from the grate and fed into the additional devices by special transporting arrangements or manually.
The German Pat. No. 532,807 discloses an apparatus for removing form sand from a casting box and for comminuting any sand clods formed by the sand removed from the box, in which the grate comprises two groups of rods extending comb-like with respect to each other and moved by eccentrics with respect to each other. This will cause horizontal movement of the sand clods, which will negatively influence the time the sand clods will remain on the grate.
An additional apparatus for removing form sand from a casting box and for further treatment of the sand is disclosed in the German Gebrausmuster 72 40 595, in which a chamber is mounted on spiral springs and oscillatable by means of an eccentric. The form sand is comminuted and classified through a sieve device having portions of different aperture size. Not sufficiently comminuted sand clods are discharged from the chamber through appropriate chutes to be subsequently further comminuted.